Full Idea
Behaviourism is false, but one is not far from the truth if one defines the mind as the cause of behaviour.
Gist of Idea
Behaviourism is false, but mind is definable as the cause of behaviour
Source
David M. Armstrong (Pref to new 'Materialist Theory' [1992], p.xvi)
Book Reference
Armstrong,D.M.: 'A Materialist Theory of Mind' [Routledge 1993], p.-8
A Reaction
As Putnam says, if you cut all the efferent (outgoing) nerves, you would have a mind with no behaviour at all. I would say my mind is full of stuff that never affects my behaviour. However, influencing behaviour is certainly the main function of a mind.